if this is a serious question, presumably it is about limits, i.e. if \(\lim_{x\to\infty}f(x)=\infty\) and \(\lim_{x\to \infty}g(x)=0\) then what is
\[\lim_{x\to \infty}f(x)g(x)\] the answer is it could be anything, it depends on \(f\) and \(g\)
the form is not determined

\[\large a \times b = c\]
\[\large a=\frac{c}{b}\]
\[\large b=\frac{c}{a}\]
Let a = ∞, b=0
\[\large ∞=\frac{c}{0}\]
\[\large 0=\frac{c}{∞}\]
But c/0 is undefined and so is c/∞, right?
What if c were positive? What if c were negative?

this is definitely an undefined case because any number multiplied with zero become zero and any number multiplied with infinity become infinity that's why both of these cases are possible here therefore we cannot consider one these case separately. thus this is an undefined case.

@Jemurray3 I don't think there's anything serious going on.
Unkle came up with a cute link to slopes of parallel lines, but made the error in saying that vertical lines have a slope, m=∞, which, of course, is false.